1. The map projections represent simplified versions of the Earth, or other space objects. While they are made to give us the best possible representation of what is depicted on them, they are still too small, and too simplified, to be able to depict the object as it really is in the nature. As one of the biggest problems is balancing the form and size of the map, with the practical aspect of its usage, and the real shapes and forms, they exhibit distortions. The distortions tend to be large with the increase of latitude, while the lower latitudes have little to no distortions.
2. The legend is one of the most important elements on the maps. It gives us all the basic and important information about the map, how it should be read, and what is the meaning of the colors, drawings, shapes etc. By using the legend, the reader can easily see the map in its true light, and very importantly, be able to see the things on it properly and as they were meant to be. If the reader avoids the legend, then a problem can occur, as the chances are the lot of things on the map will either not be clear to the reader, or will be confused with the reader's subjective view of things.
3. Both the latitude and longitude are man-made creations. They are parallel lines across the Earth that the people made them out for their own purposes and practical usage. The difference between these two sets of lines on the planet are that the longitude goes from the Prime Meridian to east and west, and it has 180 degrees in both ways, while the latitude goes from the Equator to north and south, and it has 90 degrees in both ways. The longitude lines are in north-south direction, while the latitude lines are in east-west direction.
4. The meridian at O degrees longitude is the Prime Meridian. The parallel at O degrees latitude is the Equator. These two, the Prime Meridian and the Equator, are the two imaginary lines from which the longitudinal and latitudinal measuring starts. The Prime Meridian  goes from north to south, passing through the Arctic Ocean, North Atlantic Ocean, UK, France, the western part of North Africa, Western Africa, South Atlantic Ocean, Southern Ocean and through Antarctica. The Equator goes from east to west, and it passes though the Pacific Ocean, the Indonesian Islands, Indian Ocean, the central part of Africa, South Atlantic Ocean, and through the central part of the northern half of South America.
